Heat exchanger

ABSTRACT

Heat exchanger ( 1 ), in particular a gas condenser for a CO 2  coolant comprising at least one two-part collector chamber ( 4 ) consisting of a base ( 3 ) and a cover ( 5 ) and a heat exchanger network consisting of flat tubes ( 2 ) and corrugated ribs.

The invention relates to a heat exchanger, in particular a gas coolerfor CO₂ as coolant, according to the preamble of patent claim 1.

Heat exchangers for air-conditioning systems with R134a as coolantconsist of a heat exchanger network comprising flat tubes and of headertubes arranged on both sides of the network and possessing a circularcross section. Designs of this type had sufficient strength for thepressures occurring in a condenser. Where modern coolants, such as, forexample, CO₂, are concerned, however, considerably higher pressuresarise which can no longer be controlled by means of the conventionalheat exchanger types of construction. Extruded header tubes with anincreased wall thickness were therefore proposed in WO 98/51983, aheader tube consisting of four circular flow ducts arranged next to oneanother. The production of such an extruded header tube iscost-intensive on account of the dies required for this purpose.

Another type of header tube was proposed in DE-A-199 06 289, a headertube being constructed from extruded parts and having two circular flowducts for the coolant CO₂. Even in this type of construction, at leastpart of the header tube has to be produced by extrusion, and this has anadverse effect on the production costs of the heat exchanger (gascooler).

The object of the present invention, therefore, is to provide a heatexchanger of the type initially mentioned with a cost-effective andpressure-resistant header tube.

The solution for achieving this object may be gathered CONFIRMATION COPYfrom the features of patent claim 1.

Accordingly, the header tube is produced in two parts, that is to sayfrom a bottom and from a cover which consists of a bent sheet metalstrip in the shape of, for example, a W and which forms with the bottomtwo approximately circular flow ducts. The cover and the bottom and alsothe flat tubes inserted into the bottom are soldered to one another in apressuretight manner. A longitudinal partition of the cover/bottom actsin this case as a tie rod since it is soldered to the bottom/cover. Thistype of construction of the header box is cost-effective, since thereare no costly tools required for bending or folding the cover and thebottom.

Advantageous refinements of the invention may be gathered from thesubclaims. For example, the edges of the cover which engage over thebottom have individual tabs or brackets which engage over the bottom inits edge region and consequently bring about a prefixing of the bottomand cover before the soldering process. There is therefore no longer anyneed for an additional soldering device in order to solder the heatexchanger. Increased pressure stability is achieved when the bottom isof concave design. It is advantageous, furthermore, that the middle webor the longitudinal partition has in the region of the flat tube endsindentations which allow an outflow of the coolant from the flat tubesand an overflow of the coolant from one longitudinal duct into theother. This affords diverse possibilities for routing the flow of thecoolant, in particular in conjunction with partitions runningtransversely. It is also advantageous if a step as bearing means for thebottom is provided on the inside of the cover edges. A defined bearingsurface is thereby obtained during the assembly of the cover and bottom.Finally, the number of longitudinal ducts of the header box may bemultiplied by the cross-sectional shape of the cover being a WW-shape ora multiple-W shape. In each case two additional longitudinal ducts arethereby provided, that is to say a larger volume for the coolant is madeavailable, as required. It may likewise be advantageous in this case toprovide two or more flat tube rows instead of only one flat tube row.

Exemplary embodiments of the invention are illustrated in the drawingsand are described in more detail below. In the drawings:

FIG. 1 shows a perspective part view of a single-row gas cooler,

FIG. 2 shows a longitudinal section through the gas cooler according toFIG. 1,

FIG. 3 shows a section along the line III-III in FIG. 2,

FIG. 4 shows a second exemplary embodiment of a gas cooler with a stepin the cover edge,

FIG. 5 shows a longitudinal section through the gas cooler according toFIG. 4,

FIG. 6 shows a third exemplary embodiment of a two-row gas cooler with afour-duct header box, and

FIG. 7 shows a further perspective view of the gas cooler according toFIG. 6.

FIG. 1 shows a part view of a condenser or gas cooler 1, such as may beused preferably in an air-conditioning system of a motor vehicle, saidair-conditioning system being operated with the coolant CO₂. As is knownper se, the gas cooler 1 has a heat exchanger network, of which onlyflat tubes 2 are partially illustrated here, said flat tubes beingreceived with their tube ends 2 a by a bottom 3 of a header box 4.Between the flat tubes 2 are located corrugated ribs, not illustrated,for enlarging the air-side heat exchange surface. The header tube 4consists, furthermore, of a cover 5 of W-shaped or M-shaped design whichengages behind the bottom 3 with brackets or tabs 6 arranged at theedge.

The W-shaped or M-shaped cover is designed in such a way that alongitudinal partition is formed such that regions of the cover touchone another and are soldered to one another. A double-walled partitionis thus formed.

Instead of the cover, the bottom may also have the partition.

FIG. 2 shows a section through the gas cooler 1 according to FIG. 1,specifically in parallel between two flat tubes 2. Clearly recognizablein this cross section is the W-shape or M-shape of the cover 5 which isbent from a sheet metal strip and which has two outer edge regions 7, 8and a middle web 9 which is produced as a fold and which forms alongitudinal partition running in the longitudinal direction of theheader box 4 and consequently subdivides the header box 4 into twolongitudinal ducts 10, 11. The bottom 3 is of concave design, that is tosay is curved outward. The middle web 9 has a web back 12 which liesover its full area on the bottom 3 and is soldered to the latter so asto form a tie rod. The bottom 3, which in each case projects somewhatbeyond the narrow sides of the flat tubes 2, has tabs 6, 13 engagedbehind it in these regions, with the result that a fixing of the cover 5and bottom 3 is brought about.

FIG. 3 shows a section along the line III-III in FIG. 2, the flat tubes2 being hatched in a simplified illustration. In actual fact, the flattubes 2 have a multiduct cross section which is produced by extrusion.The flat tube ends 2 a are received in corresponding orifices 3 a of thebottom 3 and project into the interior of the longitudinal ducts 10, 11.In this region around the flat tube ends 2 a, the longitudinal partitionor the middle web 9 is provided with archway-shaped indentations 14, sothat its U-shaped gap 15 remains around the flat tube ends 2 a. By meansof this gap 15, on the one hand, coolant can emerge from the flat tubes2 and, on the other hand, coolant can flow from one longitudinal duct 10over into the other longitudinal duct 11, or vice versa. The gaps 15 arethus overflow orifices between the two longitudinal ducts 10, 11.

FIG. 4 shows a second exemplary embodiment of a gas cooler 16 with acover 17 of W-shaped design and with a planar bottom 18.

FIG. 5 shows a longitudinal section through the gas cooler 16 accordingto FIG. 4. The cover 17 has two edges 19, 20, on the inside of which areintegrally formed steps 21, 22 which serve as bearing means for thebottom 18. On the side facing away from the steps 21, 22, the bottom 18has engaged behind it tabs 23, 24 which project from the edges 19, 20.

FIG. 6 and FIG. 7 show a third exemplary embodiment of a gas cooler 25with two rows of flat tubes 26, the ends of which are received by aplanar bottom 27 of a header box 28. The latter has a cover 29 which isbent and folded from a sheet metal strip and which has the shape of adouble W, that is to say three middle webs 30 which subdivide the headerbox 28 into four longitudinal ducts 31. As already described above, thiscover 29 also has steps 32 for the bearing of the bottom 27 which islikewise fixed by means of tabs 33.

By virtue of this multiduct design, a larger volume for the header box28 is formed and, at the same time, the pressure stability required forthe high internal pressures is ensured.

1. A heat exchanger, with at least one two-part header box and with aheat exchanger network preferably consisting of flat tubes and ofcorrugated ribs, the at least one header box consisting of a bottom andof a cover, and the bottom having orifices for the reception of ends ofthe flat tubes, the bottom being connected to the cover in a fluid tightmanner, the header box having at least one longitudinal partition forforming at least two longitudinal ducts, the cover being designed insuch a way that the longitudinal partition is formed by two regions ofthe cover which are oriented essentially in parallel.
 2. The heatexchanger as claimed in claim 1, characterized in that the two regionsoriented essentially in parallel touch one another.
 3. The heatexchanger as claimed in claim 1, characterized in that the two regionsoriented essentially in parallel are connected, such as, for example,soldered, to one another.
 4. The heat exchanger as claimed in claim 1,characterized in that a longitudinal partition is produced as abent-round or folded sheet metal wall.
 5. The heat exchanger as claimedin claim 1, characterized in that a longitudinal partition is producedas a fold.
 6. The heat exchanger as claimed in claim 1, characterized inthat the cover has one, two, three or more partitions.
 7. The heatexchanger as claimed in claim 1, characterized in that the cover engagesover the bottom at the edge.
 8. The heat exchanger as claimed in claim1, characterized in that the bottom engages over the cover at the edge.9. The heat exchanger as claimed in claim 1, characterized in that thebottom is of concave design and has a curvature which points outwardfrom inside the header box.
 10. The heat exchanger as claimed in claim1, characterized in that the bottom is of convex design and has acurvature which points inward from outside the header box.
 11. The heatexchanger as claimed in claim 1, characterized in that the cover or thebottom engages behind the bottom or the cover at at least one edge,advantageously at two edges.
 12. The heat exchanger as claimed in claim1, characterized in that the bottom or the cover is designed with tabswhich engage behind the cover or the bottom at the edge.
 13. The heatexchanger as claimed in claim 12, characterized in that the tabs arearranged between the flat tubes.
 14. The heat exchanger as claimed inclaim 1, characterized in that the at least one longitudinal partitionhas recesses or indentations.
 15. The heat exchanger as claimed in claim14, characterized in that the partition has recesses or indentationsinto which flat tube ends at least partially engage or project.
 16. Theheat exchanger as claimed in claim 14, characterized in that thepartition has recesses or indentations into which no flat tube endsproject.
 17. The heat exchanger as claimed in claim 15, characterized inthat free regions, such as, for example, gaps, are left between theindentations and the flat tube ends.
 18. The heat exchanger as claimedin claim 17, characterized in that the free regions are designed asU-shaped gaps.
 19. The heat exchanger as claimed in claim 17,characterized in that the free regions are designed partially as stopsfor the tubes.
 20. The heat exchanger as claimed in claim 1,characterized in that the edges of the cover or bottom have on theinside steps which run in the longitudinal direction and against whichthe bottom or cover bears.
 21. The heat exchanger as claimed in claim 1,characterized in that the cover has further longitudinal partitions forforming further longitudinal ducts.
 22. The heat exchanger as claimed inclaim 1, characterized in that the further longitudinal partitions orindividual longitudinal partitions have no recesses or indentations. 23.The heat exchanger as claimed in claim 1, characterized in that thefurther longitudinal partitions or individual longitudinal partitionshave recesses or indentations which, however, do not serve for theoverflow of a fluid.
 24. The heat exchanger as claimed in claim 1,characterized in that the flat tubes (26) are arranged in two or morerows.